* Police investigate murder of soldier in London street
* Friend tells BBC spies tried to recruit one of suspects
* Counter-terrorism police arrest 31-year-old man at BBC
* Interior ministry has no comment on veracity of claims
British counter-terrorism police arrested a man at the BBC's headquarters after an interviewee said that security services tried to recruit one of the two suspects in the murder of a soldier in London.
Michael Adebolajo, 28 and Michael Adebowale, 22, are under armed guard in hospital after being shot and arrested by police following the murder of 25-year-old Afghan war veteran Lee Rigby on Wednesday. They have not yet been charged.
A man identified by the BBC as Abu Nusaybah told its flagship news programme "Newsnight" that intelligence officers had approached Adebolajo six months ago to see if he would work for them as an informant. He said Adebolajo had refused.
BBC reporter Richard Watson, who conducted the interview, said police were waiting to arrest Nusaybah after the interview had finished on Friday. The pre-recorded interview was broadcast later that evening.
London's Metropolitan Police said counter-terrorism officers had arrested a 31-year-old man at 2030 GMT on "suspicion of the commission, preparation or instigation of acts of terrorism".
A police spokesman said the arrest was made at the BBC building, but he did not confirm the man's identity. He also said the arrest was not directly linked to the soldier's murder. He would not comment on the BBC interview.
A source close to the investigation told Reuters earlier this week that both attackers were known to Britain's MI5 internal security service. However, intelligence officers thought both men did not pose a serious threat.
Prime Minister David Cameron has said a parliamentary committee will investigate the security services' role.
In his BBC interview, Nusaybah alleged that intelligence officers visited Adebolajo's London home after the suspect made a trip to Kenya last year. Nusaybah said his friend had been arrested and questioned in Kenya.
"He mentioned initially they wanted to ask him if he knew certain individuals," Nusaybah told the BBC. "But after him saying that he didn't know these individuals, what he said was they asked him if he would be interested in working for them. He refused to work for them."
Asked about Nusaybah's comments, a Home Office (interior ministry) spokesman said it never commented on security matters.
Witnesses said two men used a car to run down Rigby outside Woolwich Barracks in southeast London and then attacked him with a meat cleaver and knives, before being shot by police.
The pair told bystanders they were acting in revenge for British wars in Muslim countries.
There was no word on any charges being laid against Adebolajo and Adebowale.